| Recent years, with the people’s living standards improved greatly, communication is not onlyrequired to provide a wide range of communications business, but also required to ensure the highquality of the communication system. The people’s ever-increasing needs will inevitably lead tothat Communication system will be further improved and upgraded. In October2005theITU-RWP8F17th meeting, the4G technology has been officially named as IMT-Advanced byITU (International Telecommunication Union). It is necessary requirement for4G system whichwill obtains a wide range of communications business and higher quality, Thus the linearmodulation technique, such as quadrature phase shift keying (QPSK),64-phase quadratureamplitude modulation (64QAM)) and multi-carriers modulation technique (orthogonal frequencydivision multiplexing, OFDM) have been widely used. High efficiency, high speed and a widerange business must be based on the high quality of Communication system. RF power amplifiersmust offer higher linearity and reduce the influence of nonlinear distortion. So the linearizationtechnology of RF power amplifier is one of the key points of communication system.The main research part of this thesis is the linear technology which based on IMT-Advancedsystem. First of all, it mainly talked about the causes and characteristics of nonlinear distortion.And then expounds the various common linearization technology, compares the advantages anddisadvantages. The thesis mainly research on the cause and difference between the static nonlineardistortions and the dynamic nonlinear distortions caused by memory effects. Then it discussed thedifference pre-distortion technologies between in the static nonlinear distortion and the dynamicnonlinear distortions conditions and its compensation effect. Then it discusses the influence of thememory effects and the digital pre-distortion technologies which are fit for RF power amplifierwith memory effects. Finally the experiment is tested in test platform of IMT-Advanced system.The test signal employed is a single-carrier IMT-Advanced signal of20MHz bandwidth, which isin accord with the standard of IMT-Advanced system, generated by Agilent ADS software andthen reduced the PAPR processing.The test results conclude that the memory effects of IMT-Advanced power amplifier arerelatively strong and cannot be ignored. The digital pre-distortion techniques provide excellentperformance in compensating the signal nonlinear distortion caused by memory effects of TD-LTE power amplifiers, especially when a Augmented Hammerstein pre-distorter is applied, which hasbeen widely utilized and developed further in the future. |
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